1. Field of the Invention
This invention relates to a vehicle that has at least one electrical traction motor, at least one additional user of electrical energy, a traction control system and a source of electrical energy. It further relates to a method for the operation of a vehicle that has an electric motor traction drive, whereby by means of a vehicle control system, during traction operation, electrical energy from an energy source is fed into at least one electrical traction motor and into at least one additional user of electrical energy.
2. Description of the Prior Art
If the electrical energy source fails in a vehicle that has an electric motor traction drive, neither the traction motor nor the electrical users are any longer supplied with electrical energy. If the user in question is a safety-relevant component or system, such as the electric motor of an electro-hydraulic steering system, for example, it is necessary to take measures to respond to this contingency and to ensure that the vehicle can still be steered until it comes to a stop.
In practice, this is achieved by taking energy from a second energy supply system that has its own energy storage mechanism and feeding said energy to the user. For an electro-hydraulic steering system, for example, an emergency hydraulic power supply can be provided by means of a hydraulic reservoir, by means of which the vehicle can still be steered for a certain length of time, although the steering force that must be applied is greater. In Diesel-electric vehicles, moreover, it is possible in the event of the failure of the Diesel engine and/or of the electrical generator that is driven by it, to take electrical energy from the starter battery.
Finally, as a result of a redundant design of the energy supply system, the energy supply can be guaranteed even in emergencies, although providing such a capability is complex and expensive.
The object of this invention is to make available a vehicle and a method of the type described above, by means of which the safety-relevant electrical users can be supplied with electrical energy even in the event of a failure of the energy source.
The invention teaches that this object can be accomplished on a vehicle of the type described above if the traction motor is effectively connected with the vehicle control system so that in the event of a failure of the electrical energy source, the vehicle is automatically braked regeneratively and the user is supplied with electrical energy by the traction motor which is operating in the regenerative mode.
The method taught by the invention accomplishes this object because, in the event of a failure of the electrical energy source during traction operation, the vehicle is automatically braked regeneratively, whereby electrical energy is fed to the user by the traction motor operating in the regenerative mode.
The teaching of the invention is accordingly to convert the kinetic energy of the moving vehicle into electrical energy, and thus to continue supplying the users with power until the vehicle comes to a stop.
It is, therefore, possible to securely bring a vehicle that operates on battery electric power, for example, to a stop when its traction battery fails (e.g., the battery contacts open accidentally). The invention makes it possible to do without a second energy supply.
The vehicle is advantageously braked regeneratively by the vehicle control system so that the electrical energy generated by the traction motor is sufficient to operate all the safety-relevant users.
In one advantageous configuration of the invention, the electrical energy that is generated by the traction motor operating in the regenerative mode is fed into a user that is realized in the form of an electrically actuated brake (brake by wire).
As an alternative or in addition, it is possible to feed the electrical energy generated by the traction motor functioning in the regenerative mode into a user that is realized in the form of an electrical steering system.
The realization of the vehicle in the form of an industrial truck, in particular an electric fork lift truck, that has a traction battery is particularly favorable. The same is true for the use of the method taught by the invention in an industrial truck, in particular an electric fork lift truck, that has a traction battery.
Additional advantages and details of the invention are explained in greater detail on the basis of an exemplary embodiment that is illustrated schematically in the accompanying drawing.